The observation that hypoxia is a major cause of treatment resistance in head and neck cancer (HNC) has been well established for almost a decade. At PENN, we have developed invasive (based on immunohistochemistry, IHC) and non-invasive (based on PET) imaging techniques to identify the presence, level and distribution of hypoxia in tissues. The agent used is a 2-nitroimidazole agent, EF5 that was specifically developed as a quantitative hypoxia marker. We have recently shown that the IHC analysis of EF5 in HNC is prognostic for patient outcome. The overall goal of this project is to build on this observation utilizing 18F-EF5 PET imaging to determine the presence and level of hypoxia as a treatment resistance factor. In our first specific aim (SA), patients with de novo HNC will be imaged with 18F-EF5 PET to ascertain whether this signal can be used as a prognostic and predictive marker. All patients will be treated with a standard regime of surgery followed by chemoradiation therapy. Tissue collected at surgery will be used to assay hypoxia-related biological endpoints including HIF1?, proliferation (Ki67), blood vessels (CD31), apoptosis and pAkt (radiation resistance) and osteopontin (OPN) in the urine. In our second SA, we will study 18F-EF5 PET images in recurrent HNC and assess whether nelfinavir (NFV), a clinically used anti-viral therapy for AIDs, can modify tumor oxygen levels. This work is the clinical extension of published observations made in PENN radiation biology labs that NFV is a radiation sensitizer. Biological and patient outcome endpoints, similar to SA1, will be explored. The long-term application of SA1 is to use the levels and patterns of hypoxia for individualized radiation dose escalation. This is particularly relevant at our institution as we will open our Proton therapy facility in 2010. We hope that positive results with NFV (e.g. tumor re-oxygenation) as studied in SA 2, will open a new avenue for adjuvant therapy in HNC. PUBLIC HEALTH RELEVANCE: Hypoxia has been shown to limit the efficacy of all types of cancer therapy including radiation, chemotherapy and even surgery (because hypoxic tumors are more likely to invade and metastasize). In order to overcome these limitations, it is critical to be able to diagnose the presence, patterns and levels of hypoxia in individual patient tumors. The use of the hypoxia imaging agents EF5 (in tissue sections) and 18F-EF5 for PET scanning will define which patients and what therapies will be most effective in order to improve patient outcome and quality of life.